For the sake of good optical efficiency, the reflectivity of mirror surfaces in solar collectors should be as high as possible. Until now, most solar reflectors have used aluminum with efficiencies in the 80-90% range. Even the best material, silver, allows reflectivities only up to 95%. With total internal reflection (TIR), on the other hand, effective reflectivity is limited only by absorption in the transparent medium, and absorption losses can be kept well below 5%. Since TIR occurs only under special circumstances, its use for solar energy collectors may be somewhat limited. One particular example, proposed by Winston, utilizes a solid refractive medium with TIR as described in Applied Optics, February 1976. His device is well suited for solar cells, and can also be used to build spectrally selective windows for thermocollectors. However, in most solar-thermal applications, the dimensions of aperture and absorber rule out this design because a prohibitively large quantity of material would be needed.
It is therefore an object of this invention to provide an improved reflective wall for solar energy concentration collection device.
Another object of this invention is to provide an improved reflective wall for solar energy collection and concentration devices having a high reflectivity.